Lew optimistic of TPP tick: Turnbull

US Treasury Secretary Jack Lew is optimistic Congress will sign off on a major 12-nation trade deal, Prime Minister Malcolm Turnbull says.

The pair had a 30-minute phone discussion on Sunday night local time in which they spoke about the Trans-Pacific Partnership.

"The treasury secretary is optimistic Congress will ratify the TPP during the lame duck," Mr Turnbull later told reporters on the floor of the New York Stock Exchange, referring to the time between the November election and January.

"But it obviously remains to be seen."

Mr Turnbull said he told him the TPP is more than just about economics or trade.

"It is a statement of America's commitment to the region," he said.

Both presidential hopefuls Donald Trump and Hillary Clinton oppose the trade pact, meaning it's chances of passing after January are all but dead.